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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christian Brauner <christian@brauner.io>
Cc: keescook@chromium.org, linux-kernel@vger.kernel.org,
	ebiederm@xmission.com, mcgrof@kernel.org,
	akpm@linux-foundation.org, joe.lawrence@redhat.com,
	longman@redhat.com
Subject: Re: [PATCH 1/2] sysctl: add overflow detection to proc_get_long()
Date: Mon, 15 Oct 2018 01:03:10 +0100	[thread overview]
Message-ID: <20181015000310.GX32577@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20181014185345.o6uokigiytqugg6v@brauner.io>

On Sun, Oct 14, 2018 at 08:53:46PM +0200, Christian Brauner wrote:

> > Yecchh...  First of all, the cast back to unsigned long long is completely
> > pointless.  What's more,
> 
> Sorry, seriously asking: why? This was meant to handle the case where
> sizeof(unsigned long long) != sizeof(unsigned long) and I just looked at
> _kstrtoul() which does the same:
> 
> int _kstrtoul(const char *s, unsigned int base, unsigned long *res)
> {
> 	unsigned long long tmp;
> 	int rv;
> 
> 	rv = kstrtoull(s, base, &tmp);
> 	if (rv < 0)
> 		return rv;
> 	if (tmp != (unsigned long long)(unsigned long)tmp)
> 		return -ERANGE;
> 	*res = tmp;
> 	return 0;
> }
> 
> Sorry, if I'm being dense here.

C quiz:
	given that type of e1 is unsigned long long and type of e2 -
unsigned long, what conversions are going to happen in e1 == e2?

[relevant part of C standard: 6.5.9 (Equality operators),
6.3.1.8 (Usual arithmetic conversions)]

  reply	other threads:[~2018-10-15  0:03 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-14 13:25 [PATCH 0/2] sysctl: cap file-max value at ULONG_MAX Christian Brauner
2018-10-14 13:25 ` [PATCH 1/2] sysctl: add overflow detection to proc_get_long() Christian Brauner
2018-10-14 17:18   ` Al Viro
2018-10-14 18:53     ` Christian Brauner
2018-10-15  0:03       ` Al Viro [this message]
2018-10-15  4:47         ` Christian Brauner
2018-10-14 13:25 ` [PATCH 2/2] sysctl: handle overflow for file-max Christian Brauner
2018-10-14 22:13 [PATCH 1/2] sysctl: add overflow detection to proc_get_long() Alexey Dobriyan
2018-10-14 22:43 ` Christian Brauner

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